1. Field of the Invention
This invention relates to a transparent detergent bar and a method of making the same.
2. DESCRIPTION OF THE PRIOR ART
A conventional transparent detergent bar has been usually prepared by using soap of fatty acid as a base and saccharides such as glucose, fructose and sucrose and polyhydric alcohol such as glycerine, sorbitol, propylene glycol as an agent to impart transparency to the soap. Soap of fatty acid and the agent have been heat dissolved into a solvent of water-lower alcohol, poured into a frame, cooled and solidified according to the conventional framing method.
Though the transparent soap made by the conventional method has high commercial value and gives the consumers the feeling of high grade because of its transparency, the quality of the soap is substantially the same as the normal opaque fatty acid soap. The defects of the soap such as irritation to the skin because of a free alkali content and the rise of pH by hydrolysis, inferior foaming power in hard water and the formation of insoluble lime soap during use cannot be removed.
The synthetic detergent bars containing essentially of mono-salt of N-long chain acyl acidic amino acid are disclosed in U.S. Pat. No. 3,663,459. They have a mild and soft touch to the skin, good hardness and superior detergency and have not the above defects of the fatty acid soap. Their appearance, however, is opaque.
The attempt has been made to make the transparent fatty acid soap by adding monosodium salt of N-long chain acyl acidic amino acid to the base of fatty acid soap (cf. Japan KOKAI 76-24606). However transparent detergent bar of high grade consisting essentially of N-long chain acyl acidic amino acid salt has heretofore been not known.
It has been found that among the detergent bars consisting mainly of N-long chain acyl-optically active acidic amino acid basic amino acid salt, some bars containing a certain length of acyl derivatives, a certain kind of amino acids and having a certain neutralization degree are inferior to some degree in transparency. There is a tendency that said transparency is impaired when the bar is left standing in an atmosphere of high humidity.
It has not been known that the transparent detergent bar could be successfully prepared by using as the main component basic amino acid salt of N-long chain acyl optically active acidic amino acid or the mixture of said salt with urea.